Ring chromosome 13 is a rare chromosome abnormality in which the ends of chromosome 13 join together to form a ring shape. When a ring forms, there may be missing genes where the chromosome's ends fuse together. Therefore, the severity and symptoms associated with Ring chromosome 13 vary from person to person, depending on the number of genes, and specific genes, involved. Most people with Ring chromosome 13 also have cells with 46 normal chromosomes (this is called mosaicism), which can lessen the effect of the ring chromosome on growth and development. Signs and symptoms that may be present in a person with Ring chromosome 13 include developmental delay, slow growth and short stature, feeding difficulties, learning difficulties, a small head size, abnormal formation or positioning of the feet and/or toes, and/or abnormalities of the palate (roof off the mouth). Depending on how many genes are lost and how many normal cells a person has, additional features or birth defects may also be present. Ring chromosome 13 typically is not inherited, occurring sporadically during the formation of egg or sperm cells or shortly after the egg and sperm join together. In some cases, Ring chromosome 13 is inherited from a parent. Chromosome testing of parents can help determine whether the ring chromosome was inherited and whether future children have an increased chance to have a chromosome abnormality.